1. Field of the Invention
The present invention relates to a temperature sensor for detecting the surface temperature of a heating roller of a thermal fixing device in an image forming device, such as a printer, copying machine, facsimile machine, and a multifunction device.
2. Description of the Related Art
Image forming devices, such as printers, copying machines, facsimile machines, and multifunction devices include a thermal fixing device for fixing images onto the surface of a recording medium such as a paper sheet. The thermal fixing device includes a heating roller with a built-in halogen lamp or other heating source. A temperature sensor having a temperature detecting element is disposed in contact with the outer surface of the heating roller in order to detect and control the temperature of the heating roller.
FIG. 1 shows an example of a temperature sensor 260 used in a conventional thermal fixing device. The temperature sensor 260 includes a contact plate 265 and a temperature detecting element 264. The contact plate 265 is substantially rectangular in shape. The temperature detecting element 264 is fixed by adhesive 264c to the upper surface of the contact plate 265 near one lengthwise end of the contact plate 265. Plate-shaped side edges 265f and 265g are disposed one on each widthwise edge of the contact plate 265. The side edges 265f and 265g form an obtuse angle with upper surface of the contact plate 265 on which the temperature detecting element 264 is fixed.
As shown in FIG. 2, the temperature sensor 260 is supported in contact with a heating roller 241 of the thermal fixing device. The heating roller 241 rotates from left to right in FIG. 2 as indicated by an arrow. Although not shown in the drawings, the temperature sensor 260 is fixed to a frame of the thermal fixing device. The temperature sensor 260 is oriented with the fixed end located upstream, and the free end located downstream, with respect to the rotation direction of the heating roller 241. The lower surface of the contact plate 265, that is, the opposite that on which the temperature detecting element 264 is fixed, contacts the heating roller 241.